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 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "<div class=\"contentcontainer med left\" style=\"margin-left: -50px;\">\n",
    "<dl class=\"dl-horizontal\">\n",
    "  <dt>Title</dt> <dd>Overlay Container</dd>\n",
    "  <dt>Dependencies</dt> <dd>Matplotlib</dd>\n",
    "  <dt>Backends</dt> <dd><a href='./Overlay.ipynb'>Matplotlib</a></dd> <dd><a href='../bokeh/Overlay.ipynb'>Bokeh</a></dd>\n",
    "</dl>\n",
    "</div>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import numpy as np\n",
    "import holoviews as hv\n",
    "hv.extension('matplotlib')"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "A Overlay is a collection of HoloViews objects that are related in some way, to be displayed simultanously, overlaid in the space space. Like [``Layout``](./Layout.ipynb and unlike other containers such as [``HoloMap``](./HoloMap.ipynb) , [``GridSpace``](./GridSpace.ipynb) and [``NdOverlay``](./NdOverlay.ipynb) a ``Overlay`` is *not* dictionary like: it holds potentially heterogeneous types without any dimensioned keys.\n",
    "\n",
    "\n",
    "A ``Overlay`` cannot contain any other container type other than ``NdOverlay`` but can contain any HoloViews elements. See [Building Composite Objects](../../../user_guide/05-Building_Composite_Objects.ipynb) for more details on how to compose containers. It is best to learn about ``Overlay`` and [``Layout``](./Layout.ipynb) together as they are very closely related objects that share many core concepts."
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### ``Overlay`` is a heterogeneous collection"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can build a ``Overlay`` between any two HoloViews objects (which can have different types) using the ``*`` operator:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "xvals = [0.1* i for i in range(100)]\n",
    "curve =  hv.Curve((xvals, [np.sin(x) for x in xvals]))\n",
    "scatter =  hv.Scatter((xvals[::5], np.linspace(0,1,20)))\n",
    "curve * scatter"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "In this example, we have a ``Overlay`` composed of a ``Curve`` element and a ``Scatter`` element.\n",
    "\n",
    "For more information about both ``Overlay`` and ``Layout``, see the [Composing_Elements](../../../user_guide/02-Composing_Elements.ipynb) user guide."
   ]
  }
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